Medomak River estuary (region 2) have declined sharply. This reduction may 

 have been caused by changes in the availability of eelgrass either as a 

 vegetable food or for the associated invertebrate fauna. 



In the last decade there has been a significant reduction in pollution in the 

 Penobscot and Kennebec estuaries. Whether the effect of cleaner water has 

 been favorable or unfavorable to waterfowl populations using these areas is 

 unknown . 



Although food supplies are usually adequate in high quality waterfowl 

 habitats, food supplies can change rapidly. Most inland Maine waters support 

 only small quantities of vegetative duck foods. In riverine and/or lacustrine 

 systems, sharp changes in water levels may alter food availability. 



In some rivers, dams help reduce flooding and increase minimum flows which may 

 help maintain an abundance of aquatic foods, especially for dabbling ducks. 



Weather sometimes causes high duck mortality during the breeding season. 

 Unusually low temperatures or heavy precipitation in late April, May, and June 

 may cause heavy losses of nests or young ducklings, depending upon the nesting 

 habits of the species. For example, black ducks (early nesters) are apt to be 

 affected by floods in late April and May, whereas ring-necked ducks (late 

 nesters) are more susceptible in June. 



Cold, wet weather during nesting sometimes causes high brood mortality at a 

 time in the breeding season when it is too late for renesting. Extreme 

 weather during migration might either prolong or hasten movement in spring or 

 fall. Early winter weather seems to affect black ducks and geese most by 

 icing their feeding grounds (usually mud flats). Low temperatures can 

 severely restrict black duck food availability. Black duck losses due to 

 starvation are known to occur, but it is difficult to assess because of their 

 habit of hiding and starving in a particular area even if food is available 

 nearby. 



Human Factors 



Human-made changes in habitat sometimes adversely, and severely, affect 

 waterfowl. Hunting and natural mortality have recently been shown to be in 

 balance with recruitment up to a threshold level in mallards (Anderson and 

 Burnham 1976), but what that level is for various waterfowl in Maine has not 

 been defined. Annual variation in breeding success is the major factor 

 causing variations in abundance. 



Human activities may be beneficial or harmful. The intentional management of 

 beaver and well conceived and executed nesting box programs favor some species 

 of ducks, but intensive urban and suburban development of wetland shorelines, 

 and recreation and boating activity may reduce waterfowl production locally. 

 Because of human causes it is clear that in recent decades there has been a 

 reduction in waterfowl habitat in many inland water areas of coastal Maine. 



Although hunting mortality has been shown to be largely compensatory in 

 relation to natural mortality, banding data reveal local breeding populations 

 may be subjected to excessive kill in the fall before they disperse. 



15-37 



10-80 



